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Author Topic: Feed Rate Override needs to take acceleration into account  (Read 7855 times)

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Feed Rate Override needs to take acceleration into account
« on: March 26, 2009, 05:53:41 AM »
Hi,

I have a real problem but I am not sure it belongs to Mach3 or Warp9. I am running a SmoothStepper on my mill.

When an axis is moving, sliding the FRO up or down causes such an abrupt change in velocity that I will loose steps or sometimes totally loose coupling (is that the right word) with the stepper phases. Adjusting the FRO appears to totally ignore the acceleration parameter and will just jump to the new speed.

It would be really great if I could get this solved. I would like to be able to take the feed rate up and down dynamically as the program is running for safety reasons, like when running close to a clamp or fixture for the first time.

Maybe there is a way I could fix this in a Macro or Brain thing?

I plan on cutting a lot tomorrow so shoot me some ideas please......
Re: Feed Rate Override needs to take acceleration into account
« Reply #1 on: March 26, 2009, 06:04:17 AM »
That reminds me of something else. When can we get acceleration to be something other than linear?

I read under the Quantum thread about "S" curves and that could really help. Most machines could probably accelerate at a higher rate as long as the acceleration decreases with velocity since the steppers loose torque with speed.

I have to keep my acceleration really low just so I can obtain high velocities for rapid moves because of this.

Maybe someone could take that portion of the code and bring it to Mach3?

Offline Hood

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Re: Feed Rate Override needs to take acceleration into account
« Reply #2 on: March 26, 2009, 11:09:50 AM »
What version of Mach and SS Plugin are you using. I have had the SS since the Beta testing days and have never had that problem, the FRO is maxed at 100% but is nice and smooth below 100%.
 As for S Curve, it will probably be added in the future but it is a long way away, if you are needing speed then the answer is to get servos I am afraid.

Hood
Re: Feed Rate Override needs to take acceleration into account
« Reply #3 on: March 26, 2009, 02:22:13 PM »
The latest R3.043.000 and SS release  SmoothStepper_Beta2_v015ogb.m3p

Are you running steppers? This wouldn't happen with Servo drives that have their own closed loop position control.

I never need to go above 100% because I am using a CAM program that takes my spindle HP into account along with the cutter and material. It really pushes the tools pretty hard so I am generally down below 80% most of the time.

Offline Hood

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Re: Feed Rate Override needs to take acceleration into account
« Reply #4 on: March 26, 2009, 02:30:24 PM »
Yes, have steppers on the Bridgeport and coil winder although I never use FRO on the coil winder, my  lathe has servos.
Certainly seems a strange one and may be related to the 043 version of Mach as it is a development version meant mainly as a test for  cutter comp and it has been known to have some weird happenings, did you have this problem with earlier revisions?
Hood
Re: Feed Rate Override needs to take acceleration into account
« Reply #5 on: March 26, 2009, 03:04:56 PM »
Yes I saw this earlier, but there where bigger problems with the SS so I wasn't focused on this just yet. I believe you have to stick with the latest experimental software for the SS drivers and features to work since they are actively being developed.

The reason I am think about this is because I would like to get/build a pendant. I would like to have a MPG and FRO knobs to make life even better now that I have a CNC mill. I figure if FRO doesn't work reliably through the GUI then it will have similar issues with a pendant.

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Re: Feed Rate Override needs to take acceleration into account
« Reply #6 on: March 26, 2009, 03:15:43 PM »
The Dev version as stated was for cutter comp alterations only, the SS will work fine with any of the last revisions. There will be big changes in Mach coming soon and I think the development of that will be advantageous to the SS and then you may well have to have the latest version of Mach. I would strongly advise against  using 043 at the moment unless you are willing to accept risks and actually there are fixes done to previous versions that I know are not in 043.

What other problems have you got with the SS?

I used a PoKeys in my pendant and had FRO from a pot and it worked every bit as smooth as from the screen.

Hood
Re: Feed Rate Override needs to take acceleration into account
« Reply #7 on: March 26, 2009, 10:31:44 PM »
There are fixes in 042 that are not in 043??? That is a bit interesting.

OK, I am downloading Mach3 R3.042.024 and will give it a try. I am getting ready to do a whole lot of cutting and I need good results.

I better setup some of my test programs to check it out.

Is there any rule as to installing software over the top of previous versions?

I usually just make a backup copy of the directory and then let the installer write over the previous version.

Curt
Re: Feed Rate Override needs to take acceleration into account
« Reply #8 on: March 26, 2009, 10:55:16 PM »
I just ran my test and 3.042 behaves the same at 3.043.000.

I call on the software gods of Mach3, please make FRO adjustments obey acceleration limits.  :'(

Thanks,
Curt

Offline Hood

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Re: Feed Rate Override needs to take acceleration into account
« Reply #9 on: March 27, 2009, 04:12:46 AM »
It works correctly for me  and so far I have not seen anyone else say otherwise, they may start now LOL
I however do not have the slider on my screenset and there is a possibility that that may make a difference, I will test it out for you when I get a chance.

As for the 043 not having fixes that the previous 042 versions have there is a reason for that, 043 was put out for  a very specific reason, it had different cutter comp code in it. Ver 043 has not changed for quite a while now where 042 versions have been updated quite a few times, that is why there are at the moment 3 revisions of Mach for download, usually there are only 2, lockdown and release candidate.

If you want to attach your xml I can possibly try out your settings on my mill to see if I have issues with them.
Hood